The bottom wall of the furnace body in this known type of ash melting furnace is inclined downwardly from the incineration ash charging side to the molten slag discharging side. And the melting chamber having a heating burner installed therein is positioned on the discharging side of the furnace body, while a preheating chamber is disposed on the charging side of the furnace body for drying and heating the incineration ashes charged into the furnace body, by the combustion exhaust gases produced in the melting chamber. Further, installed on the charging side of the furnace body are an ash charging hopper and an ash push-out device.
The bottom wall of the furnace body is straight, i.e., planar in transverse cross section.
Therefore, in the preheating chamber, the incineration ashes charged into the furnace body from the ash charging hopper by the push-out device are dried and heated by the combustion exhaust gases flowing from the melting chamber while the incineration ashes are moving to the discharging side on the inclined bottom wall of the furnace body. The thus preheated incineration ashes move into the melting chamber, where they are heated and melted by the burner installed in the melting chamber whereupon the molten ashes flow down on the bottom wall until they fall down into the cooling tank through a molten slag discharging port formed in the discharging side In the cooling tank, they are cooled and solidified.
However, since the transverse sectional shape of the bottom wall of the furnace body is straight, i.e., planar throughout the width and since transverse uniform heating by the burner is difficult, the ashes in the central region are melted quickly but the ashes on the opposite sides thereof are melted slowly.
Therefore, on the bottom wall, the rate at which the molten slag flows down varies in different regions and the slate of the discharged molten slag is not uniform. Further, since the upper surface of the bottom wall is inclined straight toward the discharging side, the residence time of ashes is short. Therefore, there is a problem that ashes tend to be discharged before they are melted and another problem is that the molten slag spreads on the entire surface of the bottom wall tending to lower the temperature of the molten slag, causing the latter to solidify more easily to block the discharging port.